diff --git a/src/span.h b/src/span.h
--- a/src/span.h
+++ b/src/span.h
@@ -6,6 +6,7 @@
 #define BITCOIN_SPAN_H
 
 #include <algorithm>
+#include <cassert>
 #include <cstddef>
 #include <type_traits>
 
@@ -27,6 +28,8 @@
     constexpr C *data() const noexcept { return m_data; }
     constexpr C *begin() const noexcept { return m_data; }
     constexpr C *end() const noexcept { return m_data + m_size; }
+    constexpr C &front() const noexcept { return m_data[0]; }
+    constexpr C &back() const noexcept { return m_data[m_size - 1]; }
     constexpr std::ptrdiff_t size() const noexcept { return m_size; }
     constexpr C &operator[](std::ptrdiff_t pos) const noexcept {
         return m_data[pos];
@@ -91,4 +94,13 @@
         v.data(), v.size());
 }
 
+/** Pop the last element off a span, and return a reference to that element. */
+template <typename T> T &SpanPopBack(Span<T> &span) {
+    size_t size = span.size();
+    assert(size > 0);
+    T &back = span[size - 1];
+    span = Span<T>(span.data(), size - 1);
+    return back;
+}
+
 #endif // BITCOIN_SPAN_H